Square finish photoengraved halftone printing plate and the method of making same



SQUARE FINISH PHOT NGRAVED HALFTONE PRINTING Au 13,1946. KERN 2,4053% PLATE AND THE METHOD OF MAKING SAME Filed Sept. 2, 1943 Patented Aug. 13, 1946 SQUARE FINISH PHOTOENGRAVED HALF- TONE PRINTING PLATE AND THE METHOD OF MAKING SAME Lawrence Kern, Philadelphia, Pa.

Application September 2, 1943, Serial No. 501,010

2 Claims. 1

My invention relates to a new and useful square finish photoengraved halftone printing plate and the method of making same, and has for one of its objects to provide an original halftone printing plate having a rounded edge.

Another object of the invention is to provide a halftone printing plate in which the printing surface, composed of dots, is rounded along the edges to produce shading off portions that result in soft line borders in the impressions.

Another object of the present invention is to provide a novel method of making a rounded edge on a halftone printing plate.

A further object of my invention is to produce a rounded edge on a halftone printing plate by beveling or cutting away portions of the back of the plate to form a relatively thin rim and turning said rim down to form a depressed border resulting in a rounded edge blending into the central printing surface.

A still further object of the invention is to produce an original photo-engraved halftone printing plate as an article of manufacture by a new method which forms a rounded edge so that the printing surface dots gradually recede from the central printing area whereby an impression made therefrom will have a soft gradually shading off border.

With the above and other objects in View this invention consists of the details of construction, combination of elements and the steps involved in the production of the printing plate, all hereinafter described and then designated by the claims.

In order that those skilled in the art to which this invention appertains may know how to make and use the same, I will describe a construction in detail and a method of producing such construction, referring by numerals to the accompanying drawing forming a part hereof, in which:

Fig. 1 is a cross sectional view of a photo-engraved halftone printing plate made in accordance with my invention.

Fig. 2 is an enlarged fragmentary sectional view of the plate after being beveled or cut away at the back.

Fig. 3 is a similar view after the rim has been turned down to provide thefinished product, and illustrating the final step of the process.

In carrying out my invention as herein embodied, 5 represents a zinc or copper plate such a generally used for square finish photo-engraved halftone printing plates. The printing surface is composed of a multiplicity of so called dots 0 which, in effect, are raised areas surrounded by etched or engraved portions. .All of this is as usual and is produced in the well known manner.

Heretofore the material of. the plate has been cut away on the face by a beveler and a trimming tool to define a border. This produces a sharp outside edge and because of the natural tendency of paper to sink down over these lower edges, it requires additional work for the printer to prevent the formation of a dark or black outline. At present the printer overcomes this difficulty, to some extent, by the overlay or underlay which reduces the pressure along the edges but very often with unsatisactory results.

I completely overcome these difficulties and eliminate the use of overlay or underlay by beveling or cutting away portions of all of the edges of the plate at the back, as shown at I, Fig. 2, thereby forming a thin rim 8. This rim 8 is bent or turned down by applying pressure, through the medium of a suitable instrumentality 9, at or adjacent the margin of the rim, but removed or spaced from the inner extremity of the beveled or cut away portion, until the lower or inner face of the outer portion of said rim becomes flush with or lies in th same plane as the back of the main portion of the plate. This produces the attaching flange l0 and the rounded edge l l between said flange and the central printing surface. The rounded edge H thereby becomes a definite part of said central printing surface and includes some of the raised area or dots so that an impression made from the plate has a soft outer edge because of the blending of the high lights with the vignettes without harsh, hard or sharp and definite lines of demarcation.

A printing plate made by my method is no more expensive than an ordinary one and is cheaper in the long run because many more impressions can be obtained therefrom since, generally, the outer edge is the part of the plate that usually wears out fastest. A highly important feature of my invention is that the troubles usually experienced by printers with the sharp edge printing plate are automatically overcome when my rounded edge printing plate is emp oyed.

Of course I do not wish to be limited to the exact details of construction herein shown and described as these may be varied within the scope of the appended claims without departing from the spirit of my invention.

Having described my invention what I claim as new and useful is:

1. The method of producing a rounded edge on an original photo-engraved halftone printing plate which consists in beveling the straight edge on the back of the plate, and then turning the edge down by suitable pressure on the printing surface to form a rounded edge that carries the dots over the edge until it softly removes itself automatically from printing contact.

2. An original photo-engraved halftone printing plate provided with a printing surface on its front face, an inclined portion of said plate bordering the central portion thereof, and an attaching flange projecting from the inclined portion, said flange and inclined portion being constructed from a thin rim produced by rabbeting the underside of the edge of the plate, which rim is subsequently bent to the desired configuration.

LAWRENCE KERN. 

